1. Field of the Invention
The present invention relates to a method for delivering all or part of a rights object (RO) to users.
2. Description of the Related Art
Currently, wireless Internet and communication technologies are rapidly advancing, and handheld or portable terminals with enhanced multimedia features are widely used in everyday life. A great number of additional features have been included with mobile phones. For example, monotone melody mobile phones are being replaced with 16-chord melody mobile phones and 32-chord melody mobile phones. More recently, mobiles phones providing 64-chord ring tones have been developed. Also, demand is increasing for mobile phone terminals with a digital camera. As these handheld or portable multimedia terminals have become increasingly sought after, industry fields or companies engaged in providing related contents or services, such as ringing sound downloads, ring back tones, entertainers' or characters' photos or pictures, and moving images such as movies and sports, are rapidly growing. In the past, content providing services were usually free of charge. However, the trend is changing toward charging for these services. At an early stage, a fundamental problem for content providers was extending their ability to prevent illegal copying of contents offered to users. To this end, the content providers and distributors have devised several mechanisms based on piracy prevention technology. Today, introduction of digital rights management (DRM) schemes that manage ROs flexibly and conveniently is growing.
While the DRM scheme has enabled encrypted content to be freely distributed to users, it prevents a recipient from executing the content before purchasing the RO associated with it. The freedom in distribution of content enables the users to forward the DRM content to friends or family who they want to share it with, thereby allowing for proliferation of high quality content, its distribution and advertising carried out by its users. In order to play the encrypted content, the recipient needs to have an RO associated with the content. In other words, the recipient is not allowed to execute the content forwarded from another user without purchasing the RO.
FIG. 1 shows a conventional process of distributing the DRM content.
A first user 101 receives encrypted content provided by a content provider 130 for execution. While the encrypted content can be freely transmitted and distributed, an RO associated with the content is needed to execute the same content. When the first user 101 requests (purchases) the RO from a rights issuer 100 in order to execute the content, the rights issuer 100 transmits the requested (purchased) RO to the first user 101 who is then entitled to execute the content and enjoy multimedia information contained therein.
Once the first user 101 is satisfied with the content as the result of executing the same and wants to share the content with a friend who is a second user 102, the first user 101 forwards the same content to the second user 102. The second user 102 needs an RO to execute the encrypted content received from the first user 101. The second user 102, holding no RO associated with the content, requests the rights issuer 100 to transmit the RO for execution. The second user 102 can receive the desired content directly from the content provider 300 as well as from the first user 101.
The conventional DRM approach shown in FIG. 1 cannot allow a service user to share a rights object needed to execute the content with another user. To address this problem, Japanese Patent Laid-open Publication No. 2003-58657 has proposed a method for sharing a license to use the content with another user that involves the following:
1. Storing information on a content license in a private area of license information database for each user or terminal;
2. Upon request for transfer from an assignor, creating an encryption key, encrypting information on a license to be transferred using the encryption key, moving the encrypted information from private area to public area, and issuing the encryption key to the assignor;
3. Delivering the issued encryption key from the assignor to an assignee;
4. Upon request of the assignee to transfer the license, authenticating the assignee by checking whether he/she has the encryption key that has been issued to the assignor; and
5. Upon this authentication, decrypting the information on the license to be transferred with the encryption key and moving the decrypted information from the public area to a private area for the assignee.
The proposed approach makes it possible for a user holding a license to execute content to transfer the license to another user. In other words, the user is allowed to share the license for the owned content with others.
In the conventional approach, however, a content license is supposed to be managed by a content provider and a server of the same, and the information on the license resides only in the server. In other words, the server must be involved in sharing the license among users. Furthermore, upon request for transfer from the assignor, the server pre-authenticates the request. That is, to transfer the license for the content to the assignee, the assignor receives an appropriate encryption key from the server and delivers the same to the assignee. The assignee is then authenticated with the encryption key for use of the content. In this way, the conventional approach requires a complicated process for transferring the license.